I. Field of the Invention
The present invention relates generally to the field of cardiac resynchronization therapy (CRT), and more specifically, to a method for optimizing the patient outcome from such therapy. The disclosed method enables physicians to improve the process of implanting and programming biventricular pacemakers/ICDs.
II. Related Art
Biventricular pacing has been recently FDA approved as a new indication of pacemaker therapy for the “resynchronization” treatment of heart failure (HF) patients with wide QRS complex on ECG (ventricular dysynchrony) or abnormal ventricular activation. Although biventricular pacing has been shown to improve HF patient morbidity or their quality of life (QOL), there has been limited success in demonstrating its effect on HF patient mortality. Several problems exist in all phases of CRT:
Implantation: Lead placement on the left ventricle is very important to optimize the right ventricular to left ventricular activation sequence, in particular the activation sequence of the left ventricle (LV), in order to facilitate wall motion and ejection fraction of the ventricle. Currently, most LV electrodes are placed transvenously via the coronary sinus and great veins to a more distal and lateral-basal portion of the left ventricle. Some LV electrode positions may be more anterior or posterior. Echocardiography has been used to assess the degree of resynchronization with respect to the sequence and timing of segmental wall motion activation and stroke volume changes prior to and after implant of the biventricular pacemaker system. The use of echocardiographic measurements during implanting of the left ventricular lead/electrode is difficult to accomplish. Echo measurements are often difficult to duplicate due to positioning of the echo probe, the assessment of diastolic function itself, and are also dependent upon expensive equipment and the requisition of experienced echo stenographers. In addition, many pacemaker follow-up centers may not have readily available, a well trained echocardiography staff. Additionally, the need to enter into a draped, sterile field area of the patient during the implant procedure is problematic.
Delay Programming: Appropriate timing between atrial and ventricular contraction is necessary to optimize ventricular filling and stroke output. Pacemaker manufacturers provide only recommended values for atrial-ventricular (AV) and interventricular (RV-LV or VV) delays that are supported by case studies or clinical studies. These are deficient because they have not been supported by any activity or exercise hemodynamic and pulmonary measurements, other than, perhaps, echo assessment at rest. Aside from resting echo measurements, there does not exist a reliable and simple technique to acutely and chronically assess the efficacy of programmed AV and VV delays. In general, some other method or approach is needed to optimize the delay values on a “per-patient” basis without programming “guesstimate” values recommended by the various pacemaker manufacturers.